A user may access a communication service developed and deployed by a service provider and/or content provider by means of a fixed mobile terminal such as a television set, a desktop computer, a tablet computer or a mobile phone. The access may be implemented by establishing a communication link between a user terminal and a service server (e.g., a content server) through a customized communication client capacity. The communication link may be established by a cable communication network such as an X Digital Subscriber Line (xDSL), a Fiber-to-the-x and a cable, and a radio communication network such as Wi-Fi, 2G, 3G and Long Term Evolution (LTE).
Digital Video Broadcasting (DVB) is one of the world's mainstream digital television standards. On the basis of an MPEG-2 audio/video data compression algorithm and a multiplexing technology, the DVB standard provides a set of complete specifications of a digital television system applicable to different media. The DVB standard also defines three channel coding and modulation schemes for media data stream transmission, namely DVB-C, DVB-S and DVB-T. In addition, the DVB standard expands a system layer of an MPEG-2 standard, and enriches network interfaces.
Dynamic Adaptive Streaming over Hyper Text Transport Protocol (HTTP) (DASH) is an adaptive bit rate streaming media technology. This technology may provide high-quality streaming media contents by utilizing a traditional HTTP Web server on the internet. The DASH technology may segment a video into multiple small file blocks on the HTTP server, each file block containing a video content lasting for a short time. These small video blocks may be parts of live broadcast video content of films (on-demand) or sport competitions lasting for multiple hours. The video may be compiled into video segments with a plurality of code rates, so as to cover different network bandwidth demands.
In a development process of the above communication service, a terminal capacity and a network environment are continuously improved, and user demands for service experience are improved. An OTT technology as represented by adaptive streaming media, is flexible for the requirement of consuming videos anytime and anywhere and traditional broadcasting technologies such as an IPTV, a digital television and a satellite television have high definition and quality guarantee of a large screen. Therefore, a comprehensive solution suitable for various scenarios may be provided by combining the OTT technology and the digital television broadcasting technology. Typically, for example, a second screen application has attracted great attention, and a user may consume personalized media information associated with a TV screen broadcast program by utilizing a smart phone, a tablet computer or other TV buddies. A service operator may transmit traditional television programs to the majority of users by utilizing a broadcast network (e.g., DVB-C digital television network), and meanwhile, internet on-demand content having a long-tail effect may be additionally delivered to a specific user group by means of an internet broadband network (OTT mode). This hybrid delivery mode may save the network investment cost, and combine the technical advantages of the broadcast network and the broadband network, thereby providing rich-content and personalized service experience for the user.
The above-mentioned hybrid delivery mode is significantly characterized by independent content source, transmission network heterogeneity, differentiated playing terminals and the like. Whether time association of a broadcast program or primary media with a broadband program or ancillary media may be established, i.e., whether synchronous playing among different content sources, different transmission formats and media contents of different playing terminals may be ensured, has become key to whether this class of applications may be accepted by a user.
Audio/video feature identification technology and application of the audio/video feature identification technology are a current direction of research for solving the problem of media content synchronization under the above-mentioned hybrid delivery mode. The audio/video feature identification technology may utilize digital features of audio/video media contents as an inter-media time synchronization reference. The audio/video feature identification technology may specifically include, but not limited to, the following technologies. (1) One technology is digital watermark technology, in which digital watermarks of an audio signal in a television program may be collected, and a time progress of a program that is currently played may be detected by utilizing program channel identifier and timestamp information in the digital watermarks, so as to acquire and synchronously play appropriate ancillary media synchronously. (2) Another technology is digital fingerprint technology, in which digital fingerprint information may be extracted from an audio/video sample, and a database may be retrieved by utilizing fingerprints to acquire media synchronization information.
However, the digital watermarks and the digital fingerprints correspond to a computer-intensive technical implementation, and depend on audio/video sample capture quality and feature extraction algorithm performances of a second-screen terminal. In addition, these technologies may be greatly influenced by environment noise and terminal capacity, and therefore application scenarios of the technologies may have a certain limitations.
Another research direction for solving a problem of media synchronization playing under a hybrid delivery mode is employing a single reference clock to deliver media composed of a broadcast network and a broadband network. In one of the methods, Program Clock Reference/Presentation Time Stamp (PCR/PTS) clock information carried in a Transport Stream (TS), for example, an MPEG-2 TS code stream, may be contained in, for example, an Internet Protocol (IP) message of a Real-time Transport Protocol (RTP) for transmission. A main defect of this solution is that the PCR clock information in the TS may be changed during demultiplexing (but, a broadband operator cannot learn of this information), so that the clock continuity cannot be maintained.